➖ Subtraction 📚 Grade 1-2 ⏱ 7 min
Subtraction Within 20: How to Teach the Facts Fast
There is no separate subtraction table — it lives inside addition. A child who knows addition already knows half of all subtraction facts.
The secret of subtraction facts
5+3=8 instantly gives 8−3=5 and 8−5=3. Three facts from one addition problem — that is a number family. Mastering addition within 20 automatically unlocks all subtraction within 20. Show the connection on five examples and the child builds families alone.
💡 The key move: show the child this link early. Speed in subtraction shoots up the moment they see that subtraction reverses addition.
Number families — the main tool
The family triangle
Three numbers: 4, 6, 10. Draw a triangle: 10 at the top, 4 and 6 at the base. Cover any corner — four facts appear: 4+6=10, 6+4=10, 10−4=6, 10−6=4.
Practice families:
3, 5, 8 → 3+5=8, 5+3=8, 8-3=5, 8-5=3
7, 6, 13 → 7+6=13, 6+7=13, 13-7=6, 13-6=7
9, 8, 17 → four facts independently
3, 5, 8 → 3+5=8, 5+3=8, 8-3=5, 8-5=3
7, 6, 13 → 7+6=13, 6+7=13, 13-7=6, 13-6=7
9, 8, 17 → four facts independently
Bridging through ten
Two-step breakdown
Take 15−8. Break it: 15−5=10, then 10−3=7. The 8 splits as 5+3 — first land on ten, then subtract the rest. The strategy rests on number bonds.
Bridge practice:
13−7: 13−3=10, 10−4=6
16−9: 16−6=10, 10−3=7
14−8: 14−4=10, 10−4=6
13−7: 13−3=10, 10−4=6
16−9: 16−6=10, 10−3=7
14−8: 14−4=10, 10−4=6
Games for practice
- "Name the third" — the leader says two numbers of a family, the child names the third
- Triangle flashcards — one side shows addition, the other subtraction
- Speed round — subtraction race: who answers first
➖ Subtraction through play!
Our game trains subtraction through pictures and instant feedback.
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